Lord Addison and Lord Salisbury (then Lord Cranborne), the Conservative leader in the House of Lords from 1942 to 1957, both with memories of the troubles leading to the passing of the Parliament Act 1911, agreed that anything promised in a party's manifesto would eventually pass; anything else would be subject to full debate. In its modern form, the convention still permits the offering of reasoned amendments to a motion for second reading of a Government bill, provided such amendments are not wrecking amendments designed to destroy the bill.

In 2006, Tony Blair appointed Lord Cunningham of Felling to chair a joint committee of both Houses of Parliament to investigate possibilities of formalising numerous conventions including the Salisbury Convention.[4]